1. Field of Invention
This invention relates primarily to the reactions between the hull of a watercraft and the fluid flow.
2. Prior Art
A prior art search did not find any pertinent reference involving this invention. This invention deals with the fluid flow resulting from a moving watercraft. Generally, watercrafts are a type of waterborne vessels that have a hull and a deck; the hull interacts with the water as the waterborne vessel moves; and the operator, or passengers, occupies the deck. As the watercraft moves through the water, a fluid flow is generated proximate to the hull. The fluid flow characteristics around the hull are normally related to the morphology of the hull. The morphology is described by parametric constraints and some of these constraints include: the precise geometry of the hull, the beam to length ratio, the prismatic coefficient, the beam of waterline, and other factors describing the hull's form.
Marine engineering is a broad subject and all the variables, factors, circumstances and exceptions cannot be fully discussed in this disclosure. Generally, the operating conditions of the hull dictate the morphology of the hull. For example, hulls designed for hydroplaning have larger beam to length ratio than non-hydroplaning hulls. Most hulls are static structures, namely their parametric properties are fixed, and the geometry of the hull is designed for a particular operating condition, such as hydroplaning or low speed cruising. The specific operating conditions influence the design of the hull (i.e. Froude number, drag characteristics, displacement requirements, etc), and the resulting fluid flow characteristics.
Succinctly, the fluid flow characteristics are generally related to the morphology of the hull. This is a limitation of the current art where the fluid flow characteristics are generally rigidly related to the parametric properties of the hull. That is, properties such as beam to length ratio and hull geometry, which dictate the performance of the vessel. The apparatus of this invention addresses this limitation by interacting between the hull and the fluid flow in a dynamic manner.
As demonstrated in the primary embodiment, this invention is implemented using vented hull technology. The vented hull embodiment is chosen to demonstrate this invention because it has many benefits such as: a lack of added drag components, lower cost componentry, and it can easily be incorporated into hulls that use vented hull technology. Vented hull technology has a long history in modern navel architecture. As early as 1865 John Scott Russell developed the concept of “Air Lubrication”. He formed this concept by pumping air around the hull to reduce skin friction (viscous drag). This concept has been further refined over the years, and steps were later developed to assist in sucking air into the bottom of the hull (such as in the 1912 vessel “The Maple Leaf”). Some of the greatest research and development in this field was done during World War Two, and later these inventions where incorporated into seaplane hulls. These are published in the American National Advisory Committee for Aeronautics reports of that time (the NACA is the precursor to NASA).
There are many inventive refinements to the vented hull as illustrated in NACA reports and more recently in Canadian Patent No. CA 1119895 dated Mar. 16, 1982, granted to LANTZ, HARLAN G., for “MULTIPLE STEP VENTED HULL”. These refinements deal primarily with skin friction (viscous drag); aeration is used to reduce the surface area of the hull with respect to water flow. As a consequence of aeration, the fluid flow is manipulated as a secondary effect, and in this example, the fluid flow characteristics are still passively related and directed by the morphology of the hull.
The primary modality of this invention is with respect to viscous drag and as a consequence of using this invention the fluid flow characteristics can be manipulated. This invention also relates to the wave drag. There are two major components of hydrodynamic drag on the surface of a watercraft: wave drag, and viscous drag. There are many theories that explain the various aspects of the fluid flow characteristics, however, this invention is based on three fluid mechanic theories: wave theory, vortex sheet theory and the law of wall. The invention has at least three modalities based on the above theories, as mentioned wave theory, vortex sheet theory and the law of wall. The apparatus of this invention can be reconfigured to operate based on these modalities. The third modality (law of wall) is implemented using a method based on Walsh and Weinstein (1978-refer to information disclosure statement).
The major deficiencies with the prior art addressed by this invention are: the manipulation of the fluid flow characteristics over a wide Froude number range (this apparatus can be reconfigured to operate with a variety of modalities), the dynamic interaction between the hull and the fluid flow, the flexibility to be implemented in a variety of ways that do not require vented hull technology, and a wide variety of tuning methods that effect the performance (i.e. drag, efficiency and the handling of the vessel). There are many secondary effects that depend upon the actual implementation method; some of these will be elaborated in the alternative embodiment section of this disclosure, especially the auxiliary benefits of this apparatus with respect to viscous drag.